Neutral pose for animation
You can first store the expected neutral pose to pose library for further use.


Go to Object Data tab,  Click  button in Pose Library;
Click  on the right-hand side to add/store pose based on current pose;
Adjust the armature to the expected neutual pose;
Click  again to store it.


Then you can apply either one of them back to the armature object by clicking  on the right-hand side.



You can press Ctrl A > Apply Pose as Rest Pose, if you want to apply the neutral pose to rest pose (the real zero transformation, not offset) by then.